the google definition is: dues ex machina fallacy is the use of a “god-like” character or plot devixe that acts in a way that makes a problem or conflict seem insoluble, and thus forces the story into an unsatisfactory resolution.

Its a VERY common mistake in scifi or fantasy when the author has a complex world.

No one does it intentionally but it tends to happen when the author knows more about the tech and world than the reader (always happens) but fails to descirbe the plot point as common factor in the world and then some how its used to save the day.

In the case of a bitcoin story an audience of bitcoiners might read through the ex machina but an average reader would not.